I've looked at yokee (www.yokee.tv) that stream youtube video of a karaoke and record you singing.
furthermore - there is fusic (fusic.com) that stream music videos and record you over them.
my question - is it free to stream any video from youtube while using the input from the user (voice / video)? Do they have to pay for every play? can they manipulate the stream (like changing the playing speed of the video)?